Wholly aromatic polyester resins long have been known. For instance, 4-hydroxybenzoic acid homopolymer and copolymers have been provided in the past. Those wholly aromatic polyesters normally encountered in the prior art have tended to be somewhat intractable in nature and to present substantial difficulties if one attempts to melt process the same while employing conventional melt processing procedures. Such polymers commonly are crystalline in nature, relatively high melting or possess a decomposition temperature which is below the melting point. Other amorphous wholly aromatic polyesters when molten frequently exhibit an isotropic melt phase. With the crystalline polymers molding techniques such as compression molding or sintering may be utilized; however, injection molding, melt spinning, etc., commonly have not been viable alternatives or when attempted commonly have been accomplished with difficulty.
Representative publications which discuss wholly aromatic polyesters include: (a) Polyesters of Hydroxybenzoic Acids, by Russell Gilkey and John R. Caldwell, J. of Applied Polymer Sci., Vol. II, Pages 198 to 202 (1959), (b) Polyarylates (Polyesters From Aromatic Dicarboxylic Acids and Bisphenols), by G. Bier, Polymer, Vol. 15, Pages 527 to 535 (August 1974), (c) Aromatic Polyester Plastics, by S. G. Cottis, Modern Plastics, Pages 62 to 63 (July 1975); and (d) Poly(p-Oxybenzoyl Systems): Homopolymer for Coatings: Copolymers for Compression and Injection Molding, by Roger S. Storm and Steven G. Cottis, Coating Plast. Preprint, Vol. 34, No 1, Pages 194 to 197 (April 1974). See also, U.S. Pat. Nos. 3,039,994; 3,169,121; 3,321,437; 3,549,593; 3,553,167; 3,637,595; 3,651,014; 3,723,388; 3,759,870; 3,767,621; 3,778,410; 3,787,370; 3,790,528; 3,829,406; 3,890,256; and 3,975,487.
Also, it more recently has been disclosed that certain polyesters may be formed which exhibit melt anisotropy. See, for instance, (a) Polyester X7G-A Self Reinforced Thermoplastic, by W. J. Jackson, Jr., H. F. Kuhfuss, and T. F. Gray, Jr. 30th Anniversary Technical Conference, 1975 Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., Section 17-D, Pages 1 to 4, (b) Belgian Pat. Nos. 838,935 and 828,936, (c) Dutch Pat. No. 7505551, (d) West German Nos. 2520819, 2520820, 2722120, 2834535, 2834536 and 2834537, (e) Japanese Nos. 43-223; 2132-116; 3017-692; and 3021-293, (f) U.S. Pat. Nos. 3,991,013; 3,991,014; 4,057,597; 4,066,620; 4,067,852; 4,075,262; 4,083,829; 4,093,595; 4,118,372; 4,130,545; 4,130,702; 4,146,702; 4,153,779; 4,156,070; 4,159,365; 4,161,470; 4,169,933; 4,181,792; 4,183,895; 4,184,996; 4,188,476; 4,201,856; 4,219,461; 4,224,433; 4,226,970; 4,230,817; 4,232,143; 4,232,144; 4,238,598; 4,238,599; 4,238,600; 4,245,082; 4,245,084; 4,256,624; 4,265,802; (g) U.K. Application No. 2,002,404; and (h) European Patent Applications 0008855, 0018145. See also commonly assigned U.S. Ser. Nos. 109,575, filed Jan. 4, 1980 (now U.S. Pat. No. 4,285,852); 128,759, filed Mar. 10, 1980 (now U.S. Pat. No. 4,299,756); 128,778, filed Mar. 10, 1980 (now U.S. Pat. No. 4,279,803); 169,014, filed July 15, 1980; and 194,196, filed Oct. 6, 1980.
In commonly assigned U.S. Pat. No. 4,184,996 is disclosed a wholly aromatic polyester which consists essentially of the recurring units (a) p-oxybenzoyl moiety, (b) 2,6-dioxynaphthalene moiety, and (c) terephthaloyl moiety and is free of units which possess ring substitution. As indicated in Example II of this patent, a representative sample of the polyester there claimed was melt extruded while at a temperature of about 355.degree. C.
In U.S. Pat. No. 4,188,476 is disclosed an aromatic polyester consisting essentially of (a) p-oxybenzoyl units, (b) terephthaloyl units, (c) 2,6-dioxynaphthalene or 2,6-dioxyanthraquinone units and (d) non-symmetrical m-oxybenzoyl or 1,3-dioxyphenylene units. There is no suggestion that both 2,6-dioxynaphthalene and 2,6-dioxyanthraquinone units be provided in combination in the resulting aromatic polyester. See also European Patent Application No. 0018145 for a similar disclosure.
In commonly assigned U.S. Pat. No. 4,224,433 to the same inventors as the present application is disclosed an aromatic polyester consisting essentially of (a) 2,6-dioxyanthraquinone moiety, (b) p-oxybenzoyl moiety, and (c) aromatic diacid moiety which includes non-symmetrical 1,3-phenylene radicals and optionally some symmetrical 1,4-phenylene radicals as described.
It is an object of the present invention to provide an improved wholly aromatic polyester which is capable of readily undergoing melt processing.
It is an object of the present invention to provide an improved wholly aromatic polyester which is capable of being melt processed using standard equipment commonly selected for the melt processing of polyethylene terephthalate.
It is an object of the present invention to provide an improved wholly aromatic polyester which is capable of forming a highly anisotropic melt phase even in the absence of relatively expensive moieties which include aromatic ring substitution.
It is an object of the present invention to provide an improved wholly aromatic polyester which is capable of being melt processed to form quality fibers, films, and three-dimensional shaped articles.
It is another object of the present invention to provide an improved wholly aromatic polyester which advantageously can be melt processed at a lower temperature than the corresponding wholly aromatic polyester of U.S. Pat. No. 4,184,996 as described hereafter without resorting to the inclusion of nonsymmetrical meta disposed linkages in the polymer chain which would tend to reduce the overall melt anisotropy of the polyester.
These and other objects, as well as the scope, nature and utilization of the invention will be apparent to those skilled in the art from the following detailed description.